All structures below have central atoms which would exceed the octet rule except for a. if3 b. nf3 c. sf4 d. brf3 e. brf4

b) NF3

Explanation:

the only structure that does not exceed the octet rule ( valence shell with 8 electrons)  is  NF3 . Knowing that

- N atom had originally 5 electrons in its valence shell

- F atom had originally 7 electrons in its valence shell

since each F atom has obtained 1 electron and completed its valence shell with 8 electrons ( from 7 electrons until 8 electrons) and N has also obtained 1 electron per each F bond, that is 3 electrons, summing up from 5 to 8 and thus also completing its valence shell with 8 electrons.

in a, c, d and e the central atom receives more electrons than the required to fill the p-orbital and accommodate them in the d-orbital

the answer to your question is c